Integrated circuits (“ICs”) are incorporated into many electronic devices. IC packaging has evolved such that multiple ICs may be vertically stacked in so-called three-dimensional (“3D”) packages in order to save horizontal area on a printed circuit board (“PCB”). An alternative packaging technique, referred to as a 2.5D package, may use an interposer, which may be formed from a semiconductor material such as silicon, for coupling one or more semiconductor die to a PCB. A plurality of IC or other semiconductor die which may be of heterogeneous technologies, may be mounted on the interposer. In addition to being joined to the plurality of IC die, the interposer is also joined to the PCB and oftentimes to a package substrate disposed between the PCB and the interposer.
Many devices on one or more of the semiconductor die may cause electrical noise and/or create electromagnetic (“EM”) interference by emitting EM emissions. RF devices and inductors are examples of devices which can create electrical noise and electromagnetic (“EM”) interference. The noisy source such as an RF transmitter or receiver generates electric noise in the form of EM emissions that can propagate through air, or electrical noise in signals carried in conductive structures such as metal leads. The EM emissions and the noisy electrical signals carried in the conductive leads, can impact various other signals and devices in the interposer, the other semiconductor die coupled to the interposer, and various components in all parts of the package. Noisy electrical signals and EM emissions therefore present serious problems in semiconductor packaging.